In our review of physical nature and vital nature, we have found a non-moral action that follows the lines set down for the working of physical forces and vital forces. The first stirrings of mental force are harnessed to the vital fulfilment. If this were the entirety of our capabilities, we would have found a simple, dynamic law of existence, that would have excluded just about everything that we consider to be distinctly human. Because in the end, despite the focus we put into physical and vital actions, the one central reality that is most characteristic for humanity is our embodiment of mentality and the principles that this brings into life.
Sri Aurobindo integrates the mental principle into our view of human nature: “Man is not after all in the essence of his manhood or in the inner reality of his soul a vital and physical being raised to a certain power of mental will and intelligence.”
“But the more he looks into himself and the more he goes inward and lives intimately and preeminently in his mind and soul, the more he discovers that he is in his essential nature a mental being encased in body and enmeshed in the life activities, manu, manomaya purusha. He is more than a thinking, willing and feeling result of the mechanism of the physical or an understanding nexus of the vital forces. There is a mental energy of his being that overtops, pervades and utilises the terrestrial action and his own terrestrial nature.”
The entry of the mental force into the world brings with it another line of energy that has its own laws of action and reaction, and thus, we add in the impact of the mind’s forces to our understanding of the law of Karma.
Sri Aurobindo, Rebirth and Karma, Section II, Chapter 15, Mind Nature and Law of Karma, pg. 127, http://www.lotuspress.com/item.php?item=990117